Abstract

Recently, there has been considerable interest in developing organically functionalized siliconsurfaces for a variety of applications including sensing and nanoelectronics. In this study, a series of as-deposited, para-substituted aryl-diazonium molecular layers covalently grafted to ⟨111⟩-orientation silicon are characterized using a variety of surface analysis techniques. Collectively, these measurements suggest that relatively ideal molecular layers can be achieved with a variety of headgroups. Submonolayer amounts of silicon oxide are detected on all modified surfaces and the extent of siliconoxidation depends on the molecular substituent. For electronic device applications, it is necessary to apply contacts to molecular layers while maintaining their structural and chemical integrity. To this end, in situspectroscopies are used to infer the effects of metallization on such molecular layers. It is found that applying gold using a soft evaporation technique does not significantly perturb the molecular layer, whereas the application of copper using the same technique induces changes in the molecular vibrational spectra. Two complementary in situspectroscopic methods are analyzed to more accurately determine the chemical properties of gold/molecule/silicon junctions. The physical mechanisms of the measurements and consequences for interpretation of the resulting spectra are discussed.

Received 20 November 2008Accepted 18 February 2009Published online 06 April 2009

Acknowledgments:

The authors would like to thank Dmitri Zemlyanov for performing XPS measurements. The authors thank Christina A. Hacker, Nadine Gergell-Hackett, Curt A. Richter, and Lee J. Richter for assistance with pb-RAIRS measurements, Wenyong Wang for performing IETS measurements, and Chad Risko for DFT calculations. The authors would like to acknowledge Mark Hersam and Mark Ratner for helpful discussions. This work is supported by NSF under Grant No. ECS-0506802. A. Scott is supported by a NSF Graduate Research Fellowship.